The present invention relates to an image forming apparatus, and particularly to an improvement of a drive system of a color image forming apparatus.
By using a plurality of image forming elements and an intermediate transfer element, in a color image forming apparatus in which a single color toner image formed on the plurality of image forming elements is transferred onto the intermediate transfer element and one full color image is formed, the drive control of the plurality of image forming elements, the control of time of image formation onto the each of image forming elements and the drive control of the intermediate transfer element are very important. When the consistency is insufficient between the respective controls, or there is a difference of peripheral speed between each of image forming elements or between the image forming element and intermediate transfer element, or the time of toner image formation to each of image forming elements is out of the regular time, a color doubling or image disturbance is generated. Therefore, the high accurate control technology is used for each control.
Relating to the start stop control of each image forming element and the start stop control of the intermediate transfer element, the time control is conducted, and for the image forming element and the intermediate transfer element which are in contact with each other, the time control which starts simultaneously and stops simultaneously is conducted.
However, when the control by only the time is conducted, it has been seen that there are following problems.
It is inevitable that, between the image forming element and the intermediate transfer element, the difference of the rising characteristic and the falling characteristic is generated due to the difference of masses of themselves or the difference of inertia of these drive systems. Accordingly, the velocity change at the rising time of the image forming element and the velocity change at the rising time of the intermediate transfer element are different, and these velocity changes at the falling time are different.
Therefore, even when the image forming element drive motor and the intermediate transfer element drive motor are simultaneously turned on, the image forming element and the intermediate transfer element reach a predetermined steady state velocity through respectively different changes of velocity. Such different rising characteristics are shown in FIG. 1. It is defined that the image forming element shows the rising characteristic by a curve A, and the intermediate transfer element has the rising characteristic shown by a curve B. Both are operated at the same steady state velocity V, and in an area a, the peripheral speed of the image forming element is larger than the peripheral speed of the intermediate transfer element, and in an area b, the peripheral speed of the intermediate transfer element is larger than the peripheral speed of the image forming element. Because the image forming element and the intermediate transfer element are in contact with each other, when there is the difference between such the rising characteristics, in the area a, the intermediate transfer element and its drive system act as a load on the image forming element drive motor, and in the area b, the image forming element and its drive system act as a load on the intermediate transfer element dive motor.
Such the reverse rotation phenomenon between the peripheral speed of the image forming element and the peripheral speed of the intermediate transfer element or the phenomenon that one side peripheral speed is largely higher than the peripheral speed of the other one, is generated, and an undesirable phenomenon that an excessive load torque is burdened on the drive motor is generated. The phenomenon shown in FIG. 1 is generated not only at the start time, but also at the time of a steady state operation and stop.
Accordingly, when the design work of the drive system of the image forming element and the drive system of the intermediate transfer element is conducted, it is necessary that the power of the drive motor and the drive current of the motor are set considering not only original loads but also the above described excessive loads.
Therefore, the motor having the excessive power becomes necessary, and the excessive electric power is necessary, resulting in an increase of cost and increase of the power consumption.
To overcome the abovementioned drawbacks in conventional color image forming apparatus employing the intermediate transfer element, it is an object of the present invention to provide a color image-forming apparatus whose cost is low and power consumption is small.
Accordingly, to overcome the cited shortcomings, the abovementioned object of the present invention can be attained by image-forming apparatus and methods described as follow.
(1) An image-forming apparatus, comprising: a plurality of image-forming elements; a plurality of first driving motors, each of which corresponds to each of the image-forming elements, to drive the plurality of image-forming elements; an intermediate transfer element that is disposed opposite the plurality of image-forming elements; a second driving motor to drive the intermediate transfer element; and a controlling section to control the plurality of first driving motors and the second driving motor; wherein the controlling section controls the plurality of first driving motors and the second driving motor independently of each other, so that a first peripheral speed of each of the image-forming elements coincides with a second peripheral speed of the intermediate transfer element.
(2) The image-forming apparatus of item 1, wherein the controlling section performs controlling actions at a rise time of both the plurality of first driving motors and the second driving motor.
(3) The image-forming apparatus of item 1, wherein the controlling section performs controlling actions at a steady-state operating time of both the plurality of first driving motors and the second driving motor.
(4) The image-forming apparatus of item 1, wherein the controlling section performs controlling actions at a rise time of both the plurality of first driving motors and the second driving motor, so that a moving distance of each of the image-forming elements coincides with that of the intermediate transfer element.
(5) The image-forming apparatus of item 1, wherein, when stopping the plurality of first driving motors and the second driving motor, the controlling section turns off the second driving motor preceding to turning off the plurality of first driving motors.
(6) The image-forming apparatus of item 1, wherein either a stepping motor or a DC motor is employed for both the plurality of first driving motors and the second driving motor.
(7) An image-forming apparatus, comprising: a plurality of image-forming elements; a plurality of first driving motors, each of which corresponds to each of the image-forming elements, to drive the plurality of image-forming elements; an intermediate transfer element that is disposed opposite the plurality of image-forming elements; a second driving motor to drive the intermediate transfer element; and a controlling section to control the plurality of first driving motors and the second driving motor; wherein the controlling section controls the plurality of first driving motors and the second driving motor independently of each other, so that a first peripheral speed of each of the image-forming elements is faster than a second peripheral speed of the intermediate transfer element by a predetermined value.
(8) The image-forming apparatus of item 7, wherein the controlling section performs controlling actions at a rise time of both the plurality of first driving motors and the second driving motor.
(9) The image-forming apparatus of item 7, wherein the controlling section performs controlling actions at a steady-state operating time of both the plurality of first driving motors and the second driving motor.
(10) The image-forming apparatus of item 7, wherein, when stopping the plurality of first driving motors and the second driving motor, the controlling section turns off the second driving motor preceding to turning off the plurality of first driving motors.
(11) The image-forming apparatus of item 7, wherein either a stepping motor or a DC motor is employed for both the plurality of first driving motors and the second driving motor.
(12) A method for controlling motors equipped in an image-forming apparatus, which includes a plurality of image-forming elements, a plurality of first driving motors to drive the plurality of image-forming elements, an intermediate transfer element disposed opposite the plurality of image-forming elements, and a second driving motor to drive the intermediate transfer element, comprising the step of: controlling the plurality of first driving motors and the second driving motor independently of each other, so that a first peripheral speed of each of the image-forming elements coincides with a second peripheral speed of the intermediate transfer element.
(13) The method of item 12, wherein the controlling step is performed at a rise time of both the plurality of first driving motors and the second driving motor.
(14) The method of item 12, wherein the controlling step is performed at a steady-state operating time of both the plurality of first driving motors and the second driving motor.
(15) The method of item 12, wherein the controlling step is performed at a rise time of both the plurality of first driving motors and the second driving motor, so that a moving distance of each of the image-forming elements coincides with that of the intermediate transfer element.
(16) The method of item 12, further comprising the step of: turning off the second driving motor preceding to turning off the plurality of first driving motors, when stopping the plurality of first driving motors and the second driving motor.
(17) The method of item 12, wherein either a stepping motor or a DC motor is employed for both the plurality of first driving motors and the second driving motor.
(18) A method for controlling motors equipped in an image-forming apparatus, which includes a plurality of image-forming elements, a plurality of first driving motors to drive the plurality of image-forming elements, an intermediate transfer element disposed opposite the plurality of image-forming elements, and a second driving motor to drive the intermediate transfer element, comprising the step of: controlling the plurality of first driving motors and the second driving motor independently of each other, so that a first peripheral speed of each of the image-forming elements is faster than a second peripheral speed of the intermediate transfer element by a predetermined value.
(19) The method of item 18, wherein the controlling step is performed at a rise time of both the plurality of first driving motors and the second driving motor.
(20) The method of item 18, wherein the controlling step is performed at a steady-state operating time of both the plurality of first driving motors and the second driving motor.
(21) The method of item 18, further comprising the step of: turning off the second driving motor preceding to turning off the plurality of first driving motors, when stopping the plurality of first driving motors and the second driving motor.
(22) The method of item 18, wherein either a stepping motor or a DC motor is employed for both the plurality of first driving motors and the second driving motor.
Further, to overcome the abovementioned problems, other image-forming apparatus and methods, embodied in the present invention, will be described as follow:
(23) An image forming apparatus having: a plurality of image forming elements; a plurality of image forming element drive motors which are provided corresponding to each of the plurality of image forming elements, and which drive each of the image forming elements; an intermediate transfer element provided opposed to the plurality of image forming elements; an intermediate transfer drive motor for driving the intermediate transfer element; and a control means for controlling the image forming element driving motors and the intermediate transfer element drive motor, the image forming apparatus is characterized in that the control means controls the image forming element drive motors and the intermediate transfer element drive motor by a method by which they can be independently controlled.
(24) An image forming apparatus according to item 23, wherein the control means conducts the control at the rise time of the image forming element drive motors and the intermediate transfer element drive motor so that the peripheral speed of the image forming element and the peripheral speed of the intermediate transfer element become the same.
(25) An image forming apparatus according to item 23, or 24, wherein the control means conducts the control at the steady state operation time of the image forming element drive motors and the intermediate transfer element drive motor so that the peripheral speed of the image forming element and the peripheral speed of the intermediate transfer element become the same.
(26) An image forming apparatus according to any one of items 23 to 25, wherein the control means conducts the control so that a movement distance of the image forming element and the movement distance of the intermediate transfer element at the rise time of the image forming element drive motors and the intermediate transfer drive motor become the same.
(27) An image forming apparatus according to item 23, wherein the control means controls the image forming element drive motors and the intermediate transfer element drive motor so that the peripheral speed of the intermediate transfer element is not higher than the peripheral speed of the image forming elements by a predetermined value.
(28) An image forming apparatus according to item 23, or 27, wherein the control means conducts the control at the rise time of the image forming element drive motors and the intermediate transfer element drive motor so that the peripheral speed of the intermediate transfer element is not higher than the peripheral speed of the image forming elements by a predetermined value.
(29) An image forming apparatus according to item 23, 27 or 28, wherein the control means conducts the control at the steady state operation time of the image forming element drive motors and the intermediate transfer element drive motor so that the peripheral speed of the intermediate transfer element is not higher than the peripheral speed of the image forming elements by a predetermined value.
(30) An image forming apparatus according to any one of items 23 to 29, wherein the control means turns off the intermediate transfer element drive motor not later than the image forming element drive motor at the stop time.
(31) An image forming apparatus according to any one of items 23 to 30, wherein a stepping motor or a DC motor is used as the image forming element drive motor and the intermediate transfer element drive motor.
(32) A control method of a motor in an image forming apparatus characterized in that the image forming element drive motor and the intermediate transfer element drive motor are controlled by a method by which they can be controlled independently of each other.
(33) A control method of a motor in an image forming apparatus according to item 32, wherein the image forming element drive motor and the intermediate transfer element drive motor are controlled so that the peripheral speed of the image forming element and the peripheral speed of the intermediate transfer element drive motor at the rise time are the same.
(34) A control method of a motor in an image forming apparatus according to either one of item 32 or 33, wherein the image forming element drive motor and the intermediate transfer element drive motor are controlled so that the peripheral speed of the image forming element and the peripheral speed of the intermediate transfer element drive motor at the steady state operation time are the same.
(35) A control method of a motor in an image forming apparatus according to any one of items 32 to 34, wherein the image forming element drive motor and the intermediate transfer element drive motor are controlled so that the movement distance of the image forming element and the movement distance of the intermediate transfer element at the rise time are the same.
(36) A control method of a motor in an image forming apparatus according to item 32, wherein the image forming element drive motor and the intermediate transfer element drive motor at the rise time are controlled so that the peripheral speed of the intermediate transfer element drive motor is not higher than the peripheral speed of the image forming element by a predetermined value.
(37) A control method of a motor in an image forming apparatus according to either one of item 32 or 36, wherein the image forming element drive motor and the intermediate transfer element drive motor at a steady state operation time are controlled so that the peripheral speed of the intermediate transfer element drive motor is not higher than the peripheral speed of the image forming element by a predetermined value.
(38) A control method of a motor in an image forming apparatus according to any one of items 32 to 37, wherein the intermediate transfer element drive motor is turned off not later than the image forming element drive motor at the stop time.
(39) A control method of a motor in an image forming apparatus according to any one of items 32 to 38, wherein a stepping motor or a DC motor is used as the image forming element drive motor and the intermediate transfer element drive motor.